1. Field of the Invention
This invention relates to ink jet printing and more particularly relates to using electrorheological ink and an electrorheological (ER) valve in a printing environment.
2. Description of the Related Art
Ink jet printing is a major market within the computer industry. It reaches everything from personal computing to high-end, volume printing. Presently, two main types of ink jet printers are in use. These are 1) continuous ink jet (CIJ) printers, and 2) drop on demand (DOD) ink jet printers. While each of these printing technologies has certain advantages over the other, they also each suffer from particular disadvantages. In particular, these printing technologies as currently known suffer in the area of drop creation. In other words, these printing technologies are in certain ways inadequate in terms of creating ink drops and discharging the ink drops from a nozzle to a print surface.
The CIJ print technology generally includes a drop generator and a drop steering means. The drop generator discharges ink drops toward the print surface while the steering means steers the drops either onto the print surface or into a gutter. For example, the steering means may include two electrically charged conductive plates aligned in parallel with the path of the ink drop. In this way, the CIJ print technology maintains a continuous stream of ink from the drop generator, steering the ink drops into the gutter when not printing on the print surface. The ink in the gutter may be recycled within the printing system.
This continuous flow of ink through the nozzles of the drop generator poses several disadvantages. For example, steering the unused ink into the gutter for recycling may create a significant need for filtering the recycled ink prior to using the ink again at the drop generator. Additionally, the continuous flow of ink can have harmful effects on the nozzles, as well as the electrodes. The nozzles and electrodes may be subject to extensive contamination due to, among other things, the continuous flow of ink and the use of a significant amount of recycled ink, where the recycled ink may be less pure with each gutter and reuse cycle.
The DOD print technology has certain advantages over the CIJ print technology in that the DOD print technology does not maintain a continuous flow of ink from the drop generator. However, the DOD print technology requires a complicated drop creation system that adds cost and complexity to the DOD printers.
Other printing systems incorporate certain other technologies in an attempt to overcome some of these disadvantages of the CIJ and DOD print technologies. One technology that has been combined with certain other printing technologies was first reported in the 1940's and is referred to as electrorheology. Electrorheology is the study of fluid viscosity in the presence of an electric charge or field. Electrorheology is described in further detail in U.S. Pat. No. 3,047,507, issued to Willis M. Winslow on Jul. 31, 1962, entitled “Field Responsive Force Transmitting Compositions.”
An electrorheological fluid that changes viscosity in response to an electric field may include suspended particles within the fluid. In the presence of an electric field, these suspended particles may align themselves in a manner that increases the viscosity of the fluid. This property has also been referred to as “electro-viscosity.”
Combining electrorheology with printing technologies has presented certain problems. For example, some inventors have found it difficult to supply a sufficient voltage to an electrode in order to fully stop the flow of an electrorheological ink. The voltage necessary to slow or stop the flow of an electrorheological fluid may depend on numerous factors, including the original viscosity of the fluid, the volume of the fluid, the pressure of the fluid within a chamber, the area of the discharge aperture, the permeation of the suspended particles within the fluid, the type of electrode creating the electric field, the number of electrodes, the power supplied to the electrode(s), and so forth.
From the foregoing discussion it should be apparent that a need exists for an apparatus, system, and method that overcome the disadvantages of currently known CIJ and DOD printing techniques, as well as the previous failures to efficiently integrate electrorheological technologies into a printing system. Beneficially, such an apparatus, system, and method would avoid the complicated drop creation systems of DOD printing, overcome continuous ink streaming and the need for substantial gutter recycling, and incorporate electrorheoligical technology in a cost-effective and energy-efficient manner.